The present invention relates to a vehicle heat generator that generates heat by shearing viscous fluid with a rotor in a heating chamber and transferring the heat to a circulating fluid flowing through a heat transfer chamber. More particularly, the present invention pertains to an improvement in the flow passage of the circulating fluid.
Japanese Examined Utility Model Publication No. 7-52722 describes an auxiliary heater (heat generator), which is incorporated in a vehicle heater. The auxiliary heater includes a generally cylindrical casing (housing), which houses a cylindrical heating chamber. A plurality of outer plates are formed on the wall defining the heating chamber. A rotary shaft is rotatably supported in the heating chamber. A plurality of disc-like inner plates are fixed to the rotary shaft. Each outer plate is arranged between a corresponding pair of inner plates. That is, the inner and outer plates are arranged alternately. A viscous fluid is charged into the heating chamber such that the space between the inner and outer plates is filled with the viscous fluid. Furthermore, a coolant circuit (heat transfer chamber) extends about the heating chamber. A plurality of heat transfer fins extend along the coolant circuit.
The power of an engine is transmitted to the rotary shaft by way of an electromagnetic clutch to rotate the inner plates integrally with the rotary shaft. The rotating inner plates and the stationary outer plates shear the viscous fluid and generate heat. The fins transfer heat to an engine coolant (circulating fluid), which flows through the coolant circuit. The generated heat is used to warm the passenger compartment.
Japanese Unexamined Patent Publication No. 10-35259 describes a viscous fluid heater (heat generator) housing a heating chamber, which is defined by a cylindrical wall. A cylindrical rotor is rotatably supported in the heating chamber. A viscous fluid fills the clearance between the peripheral surface of the rotor and the cylindrical wall of the heating chamber. The viscous fluid is mainly sheared by the peripheral surface of the rotor to generate heat. A guide groove (transfer means) extends along the peripheral surface of the rotor. Rotation of the rotor forcibly moves the viscous fluid in the clearance along the guide groove toward one end of the rotor.
The coolant circuit of the auxiliary heater described in Japanese Examined Utility Model Publication No. 7-52722 forms part of a circuit that extends between the engine and a heater core. However, this publication does not discuss connection of the auxiliary heater to the other parts of the coolant circuit. An outlet pipe, through which coolant is discharged, extends radially from the front upper portion of the auxiliary heater, while an inlet pipe, through which coolant is drawn in, extends radially from the rear lower portion of the auxiliary heater. The radially extending outlet and inlet pipes restrict the layout of heater-related pipes in the engine room and thus complicate installation of the auxiliary heater in the engine room.
Further, the rotor of the auxiliary heater includes the rotary shaft and the disc-like inner plates, which are fixed to the rotary shaft. Although the rotor functions to shear the viscous fluid, the rotor does not function to move the viscous fluid in the heating chamber. However, in the viscous fluid heater of Japanese Unexamined Patent Publication No. 10-35259, rotation of the rotor moves the viscous fluid along the peripheral surface of the rotor.
Therefore, research has been carried out on rotor heat generators to control the movement of viscous fluid along the peripheral surface of the rotor by improving the circulating fluid flow passage that leads into and out of the heat transfer chamber.